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Discussion Starter · #1 · (Edited)
I have a full manual 4L80E with transbrake and fixed line pressure. The trans works great on the street. However, at the track, I'm having an issue with the 1-2 shift taking too long.

I can literally let go of the transbrake at 4500 rpm and instantly click the shifter into 2nd gear. The car will accelerate and hit the 7800 rpm rev limiter before the trans shifts.

I have datalogged trans pressure and it is around 205-210 until the release of the transbrake. Within a half of a second, it drops down to 100 psi and then recovers and starts to come back up and hits 200+ at around 3 1/2 seconds.

Is this a problem in the trans itself or is it something like needing a deeper trans pan to keep the fluid in it on hard acceleration?

Some details: 60' times in the low 1.3's at 3850 lbs, twin turbo engine on a radial, trans has: TCI billet input, steel forward drum, 36 element sprag and aluminum drum, new clutches last summer, new transbrake valve body, JD Hygard low viscosity, fluid level is correct at the pan rail, has PTC 9.5" single disc lockup converter which was fresh last summer. This trans has always taken around 2 seconds to shift from 1st to 2nd gear at WOT regardless of valve body manufacturer, regardless of builder.

Any help would be greatly appreciated.

Datalog can be seen at:
https://www.flickr.com/photos/[email protected]/

Trans pressure is downward pointing triangles. RPM is circles, driveshaft speed is upward pointing triangles
 

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I have a full manual 4L80E with transbrake and fixed line pressure. The trans works great on the street. However, at the track, I'm having an issue with the 1-2 shift taking too long.

I can literally let go of the transbrake at 4500 rpm and instantly click the shifter into 2nd gear. The car will accelerate and hit the 7800 rpm rev limiter before the trans shifts.

I have datalogged trans pressure and it is around 205-210 until the release of the transbrake. Within a half of a second, it drops down to 100 psi and then recovers and starts to come back up and hits 200+ at around 3 1/2 seconds.

Is this a problem in the trans itself or is it something like needing a deeper trans pan to keep the fluid in it on hard acceleration?

Some details: 60' times in the low 1.3's at 3850 lbs, twin turbo engine on a radial, trans has: TCI billet input, steel forward drum, 36 element sprag and aluminum drum, new clutches last summer, new transbrake valve body, JD Hygard low viscosity, fluid level is correct at the pan rail, has PTC 9.5" single disc lockup converter which was fresh last summer. This trans has always taken around 2 seconds to shift from 1st to 2nd gear at WOT regardless of valve body manufacturer, regardless of builder.

Any help would be greatly appreciated.

Datalog can be seen at:
https://www.flickr.com/photos/[email protected]/

Trans pressure is downward pointing triangles. RPM is circles, driveshaft speed is upward pointing triangles
On my Hutch 400, the trans pan is lower in the front, than the rear, with the dipstick at the front of the pan. My dipstick is notched at the pan rail. I figured that trans/converter/cooler circuit would require around 9-10 quarts. At 8 quarts it read full on the dipstick. I checked with Hutch and he said my combo should need at least 9.5 quarts. I believe the downward angle of the pan gives a false full reading, as the rear of the pan, being higher, is not as full. Under load, the dipstick and pick up filter may get uncovered, like your graph?

 

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I've encountered similar issues and mufflerguy is right. Do this:
Install a vented catch can above the trans. Plumb a line from the trans vent to the can. MAKE SURE THE CATCH CAN IS VENTED above the return line. Add 2 quarts to the trans and run it. If nothing is in the can, you are too low on fluid. Do this until the can gets fluid in it, measure how much, then you know what it wants for fluid level. In the end, plumb the line to the bottom of the can and Plumb a second line from the top of can back to the trans. Use the dipstick tube, a case fitting above the pan, something.
 

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Discussion Starter · #4 ·
Thank you both for your help. I'm hoping this is what it is. The trans works great on the street and the pressure is steady and constant. Obviously, there is no WOT in first gear on the street but everything seems to be good.

Hopefully it's just a low fluid issue.
 

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I’ve had the same issues. My early 4l80 has the big flat pan. 1.2-1.3 60ft cause pressure loss after launch. I tried the moroso deep pan and it didn’t help. All the fluid still sloshes to the rear. I’m now modifying a late model pan to fit, hoping the angle on the rear helps.
I never thought about the pan being lower towards the front effecting level. Mine is for sure.
 

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I'm having a similar problem with my 4L80E (single turbo Camaro drag racing car)--a delayed 1-2 shift only at the track. I'm wondering what your cure was. Running more fluid in the trans? Or maybe creating a baffle to slow the fluid from sloshing to the rear?

Thanks for any assistance!
Mark

I have a full manual 4L80E with transbrake and fixed line pressure. The trans works great on the street. However, at the track, I'm having an issue with the 1-2 shift taking too long.

I can literally let go of the transbrake at 4500 rpm and instantly click the shifter into 2nd gear. The car will accelerate and hit the 7800 rpm rev limiter before the trans shifts.

I have datalogged trans pressure and it is around 205-210 until the release of the transbrake. Within a half of a second, it drops down to 100 psi and then recovers and starts to come back up and hits 200+ at around 3 1/2 seconds.

Is this a problem in the trans itself or is it something like needing a deeper trans pan to keep the fluid in it on hard acceleration?

Some details: 60' times in the low 1.3's at 3850 lbs, twin turbo engine on a radial, trans has: TCI billet input, steel forward drum, 36 element sprag and aluminum drum, new clutches last summer, new transbrake valve body, JD Hygard low viscosity, fluid level is correct at the pan rail, has PTC 9.5" single disc lockup converter which was fresh last summer. This trans has always taken around 2 seconds to shift from 1st to 2nd gear at WOT regardless of valve body manufacturer, regardless of builder.

Any help would be greatly appreciated.

Datalog can be seen at:
Ed Bennick

Trans pressure is downward pointing triangles. RPM is circles, driveshaft speed is upward pointing triangles
 

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I the run you posted , it appears as though the shift command is made closely after the transbrake release according to the pressure graph, is that right?

Do you see the same pressure drop at the launch if you don't shift until later?

This is all assuming the initial statement is right of course.


Hutch
 

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You can buy a filter relocation kit that places the filter at the back of the pan-for 4l80E and TH400. We make a baffle that stops slosh towards the rear on all our T/brake drag race trans,and on our U4 trans we make a circular baffle that helps stop fluid slosh in all directions. On our U4 builds we also run a high mounted big catch can with a top filter and bottom tube inlet- it's quite common for these trans to puke a bit of oil as they get hot- any puked oil rises into the catch can but can then drain back into the trans in 'quieter' periods during the race. It works for us.
 
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